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Abstract:

A catalyst support material comprising TiO2, and optionally being
doped with a transition metal element, and a method for synthesizing the
same have been developed. The catalyst support material exhibits an
electrical conductivity comparable to widely-used carbon materials. This
is because the TiO2 present is primarily arranged in its rutile
crystalline phase. Furthermore, a mesoporous morphology provides the
catalyst support material with appropriate porosity and surface area
properties such that it may be utilized as part of a fuel cell electrode
(anode and/or cathode). The TiO2-based catalyst support material may
be formed using a template method in which precursor titanium and
transition metal alkoxides are hydrolyzed onto the surface of a latex
template, dried, and heat treated.

Claims:

1. A method of synthesizing a mesoporous catalyst support material
comprising TiO2, the method comprising:providing decomposable
polymer template particles having particle surfaces and being suspended
in an acidified alcohol medium;adding a titanium precursor alkoxide to
the medium;hydrolyzing the precursor alkoxide to deposit hydrated
titanium oxide onto the surfaces of the polymer template
particles;collecting the polymer template particles with hydrated
titanium oxide and deposited thereon;heating the polymer template
particle to decompose the polymer particles and dehydrate the hydrated
titanium oxide into a substantially anhydrous TiO2 with at least
some of the TiO2 being converted into its rutile crystal phase.

2. The method of claim 1 wherein the TiO2 is doped with a transition
metal having a valence of +5, the method comprising adding a transition
metal precursor alkoxide and the titanium precursor alkoxide to the
acidified alcohol medium and hydrolyzing the precursor alkoxides to
deposit hydrated titanium oxide doped with between about 5 and 10 mol
percent of hydrated transition metal oxide onto the surfaces of nanometer
scale polymer template particles.

5. The method of claim 1, wherein the polymer template particles are
heated at a temperature of about 500.degree. C. or higher to decompose
them.

6. A method of synthesizing a mesoporous and electrically conductive
catalyst support material comprising TiO2 doped with niobium for use
in a PEM fuel cell electrode, the method comprising:providing
decomposable nanometer scale polymer template particles having particle
surfaces and being suspended in an acidified alcohol medium;adding a
titanium precursor alkoxide and a niobium precursor alkoxide to the
medium;hydrolyzing the alkoxides to deposit hydrated titanium oxide doped
with between about 5 and 10 mol percent of niobium oxide onto the
surfaces of the polymer template particles;collecting the polymer
template particles with hydrated titanium oxide and niobium oxide
deposited thereon;heating the polymer template particles to decompose the
polymer particle and dehydrate the hydrated titanium and niobium oxide
into a substantially anhydrous TiO2 doped with a niobium oxide, with
at least some of the TiO2 being converted into its rutile crystal
phase and some of the TiO2 being converted into its anatase phase;
andheating the TiO2 and niobium oxide to further convert at least
some of the TiO2 from its anatase phase to its rutile phase and to
produce lower oxidation state titanium oxides.

13. A mesoporous catalyst support material comprising rutile TiO2
doped with a transition metal oxide such that the catalyst support
material has a general formula Ti1-xMxO.sub.y, wherein M is a
transition metal element having a oxidation state, x is from about 0.05
to about 0.10, and wherein y is variable depending on the oxidation state
of the transition metal element.

14. A catalyst support material as recited in claim 13 when carrying
catalyst particles and deposited in a fuel cell electrode.

15. The catalyst support material of claim 13, wherein the catalyst
support material comprises Ti.sub.0.92Nb.sub.0.08O.sub.2.04.

16. The catalyst support material of claim 13 further comprising titanium
oxides in a lower oxidation state than TiO.sub.2.

18. The catalyst support material of claim 13 having an electrical
resistivity below 15 Ω-cm.

19. The method of claim 1 in which the mesoporous catalyst material has
pore diameters in the range of about two nanometers to about fifty
nanometers.

20. The catalyst support material of claim 13 in which the catalyst
support material has pore diameters in the range of about two nanometers
to about fifty nanometers.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This application claims the benefit of U.S. Provisional Application
61/060,511, titled "A Method of Producing Mesoporous and Electrically
Conductive Metal Oxides for use in Electrocatalysts" and filed Jun. 11,
2008. The disclosure of that provisional application is incorporated
herein by reference.

TECHNICAL FIELD

[0002]This invention relates generally to catalyst support materials. More
specifically, a mesoporous catalyst support material comprised primarily
of rutile crystalline TiO2 has been synthesized. This microstructure
provides a catalyst support material with superior electrical
conductivity. The electrical conductivity of this material may be,
however, further improved by doping it with a transition metal element,
such as niobium, in an amount from about 5 mol percent to about 10 mol
percent of the titanium. Also, the catalyst support material's mesoporous
morphology provides it with desirable surface characteristics appropriate
to its broad application. The combination of surface area and electrical
conductivity male the catalyst support useful, for example, in fuel cell
electrodes.

BACKGROUND OF THE INVENTION

[0003]Electrocatalysts are commonly used in PEM fuel cell electrodes to
facilitate the oxidation of hydrogen gas at the anode and the reduction
of oxygen gas at the cathode. These electrocatalysts commonly comprise
nanosized platinum or platinum alloy catalyst particles supported on
larger, high-surface area and electrically conductive carbon support
particles. The purpose behind such a catalyst support structure is to
optimize the amount of three-phase boundary reactive sites per unit area
of the electrode so as to minimize catalyst loading requirements and to
increase proton mobility through the fuel cell. Indeed, carbon has long
been considered a most suitable catalyst support material because of its
low cost, good electrical conductivity, high surface area, gas-diffusible
friendly morphology, and chemical stability. An example of a specific
carbon support material widely used for preparing fuel cell
electrocatalysts is carbon black (Vulcan XC-72R).

[0004]Unfortunately, fuel cell performance setbacks that occur during
vehicle cycling or extended operation, for example, are oftentimes
partially attributed to the electrocatalytic oxidation of the carbon
support material in the fuel cell's electrodes. This is so because any
losses in carbon support material as a result of oxidation is accompanied
by an associated loss in catalyst particles which, in turn, reduces the
electrode's catalyst capacity. Attempts have thus been made to try and
fabricate catalyst support materials that can withstand corrosive fuel
cell environments and also provide comparable electrical conductivity and
surface area characteristics to those of currently-used carbon materials.
For example, TiO2-based materials are being actively investigated.
But synthesis methods have not yet been developed that can produce these
support materials such that they meet desired fuel cell operating
criteria. Some common shortcomings of these current methods are that the
synthesized TiO2 support material does not have enough open porosity
and it is not easily formed into its more electrically conductive rutile
crystalline phase. As a result existing TiO2 support materials
display relatively low surface areas and pore volumes as well as high
electrical resistivity values. It will be appreciated that the
electrically conductive character of the TiO2 support materials is
particularly significant for fuel cell applications. But the deficiencies
of relatively low surface areas and pore volumes also render current
TiO2 supports less desirable for the broad class of applications
where support material electrical conductivity is not required.

[0005]Thus, a TiO2-based catalyst support material with an acceptable
electrical conductivity and surface morphology, and a method for
synthesizing the same, are needed.

SUMMARY OF THE INVENTION

[0006]A mesoporous catalyst support material comprised primarily of rutile
crystalline TiO2 and, optionally, doped, most frequently with a
transition metal element, has been synthesized for carrying appropriate
fuel cell catalyst particles such as, for example, those of platinum or
platinum/transition metal alloys. This material's primary rutile
TiO2 crystallographic structure provides it with enhanced electrical
resistivity. The resistivity is within two orders of magnitude of the
resistivity of the industry-accepted resistivity of carbon support
materials commonly employed for fuel cells. Also, its mesoporous
morphology ensures that a sufficient porosity and surface area is
available so that it can effectively function as part of a catalyst
system including as a fuel cell electrode. If doped, the transition metal
(M) may be present in an amount from about 5 to about 10 mol percent such
that the titanium oxide material has a general formula of
Ti1-xMxO.sub.y. In this formula x is from about 0.05 to about
0.10 and y may vary based on the oxidation state of M so as to render the
material neutral and stable. This dopant range was chosen because it
helps facilitate the direct formation of rutile TiO2 at more
moderate temperatures and lower pH values, and also helps improve the
electrical conductivity of rutile TiO2 once formed by lowering its
band gap energy.

[0007]The following discussion will focus on niobium as a doping material.
Niobium, in common with other transition metals adopts multiple oxidation
states and in the practice of this invention adopts a +5 oxidation state.
While such theory is not relied upon, these characteristics are believed
to be important in conferring the desired conductivity, suggesting that
other transition metals which exhibit a large numbers of oxidation states
including a +5 oxidation state, notably vanadium, manganese, iron,
molybdenum, tantalum, tungsten and rhenium will also be effective
dopants.

[0008]The catalyst support material is formed using a template method in
which a precursor titanium alkoxide is hydrolyzed from an alcohol
suspension and deposited onto the surfaces of decomposable polymer
template particles. A doping amount of precursor transition metal
alkoxide, such as a niobium alkoxide, may also be hydrolyzed and
deposited along with the titanium alkoxide if desired. The coated
template particles are then dried, collected, and subjected to at least
two heat treatments. These two heat treatments decompose and remove the
polymer template particles and also convert the remaining Ti/Nb material
into a primarily rutile crystalline TiO2 material.

[0009]In an exemplary embodiment of the invention, the decomposable
polymer template particles may be of the latex type such as, for example,
nanometer scale polystyrene (PS) particles suspended in acidified
alcohol. Polystyrene is useful here because it readily decomposes at a
relatively low temperature (around 450° C.) and can easily be
formed into nanoscale particles sized around a few hundred nanometers or
smaller. It also decomposes in a relatively clean manner releasing only
hydrogen and hydrocarbon vapors that have minimal reactive effects on the
other materials present. Furthermore, the acidified nature of the
suspension in which the PS particles are dispersed helps keep the PS
particles thoroughly dispersed so as to maximize the available surface
area for alkoxide deposition. Also present in the suspension may be one
or more surfactants that enhance the template's affinity for precipitate
and help facilitate the dispersion of covered particles following
deposition.

[0010]A titanium precursor alkoxide, and a niobium precursor alkoxide to
serve as the transition metal dopant, may then be added to the suspension
to introduce Ti4+ and Nb5+ oxidation state metallic ions
thereto. An example of a specific titanium precursor alkoxide that may be
used here is titanium tetraisopropoxide, also referred to as TTIP,
[Ti(O(CH3)CHCH3)4]. But of course other titanium
alkoxides, such as titanium tetraethoxide and titanium tetra-n-butoxide,
may be used as well. An example of a specific niobium precursor alkoxide
that may be used here is niobium pentaethoxide
[Nb(OC2H5)5]. The titanium and niobium alkoxides may be
added in quantities that the result in the synthesized catalyst support
material being doped with niobium in an amount from about 5 mole percent
to about 10 mole percent. Furthermore, the TTIP and niobium pentaethoxide
may be added to the suspension so that, in addition to the dopant mole
ratio just mentioned, the weight ratio of PS to later formed oxides (both
of Ti and Nb) will be between 0.1 to 0.3.

[0011]The alkoxides, when added to the suspension, readily hydrolyze to
form hydrated titanium and niobium oxides when exposed to the water
present in the PS suspension. Upon formation, these hydrated oxides
precipitate out of solution as a white gel and deposit onto the surface
of the PS nanoparticles--thus mimicking a core-shell structure in which
the Ti and Nb hydrated oxides coat the PS particles to a thickness of up
to about a few tens of nanometers. The suspension may then be injected
into a spray-dryer or subjected to another appropriate technique in order
to disperse, dry, and collect the coated PS particles. Such a procedure
generally allows for a significant portion of the PS particles to be
collected as a very fine white powder.

[0012]The collected white powder may then be subjected to a first heat
treatment so as to achieve at least two objectives. First, this heating
dehydrates the hydrated titanium and niobium oxides to form substantially
amorphous anhydrous titanium and niobium oxides. This heating also forms,
however, a modest amount of TiO2 directly into its rutile
crystalline microstructure phase. It is believed that such a
transformation is assisted by the small amount of niobium present in the
TiO2 lattice system. In particular the niobium seems to function in
a catalytic manner by sufficiently lowering the activation energy for the
formation of rutile TiO2 at relatively low temperatures and less
acidic environments that normally favor exclusive anatase TiO2
formation. Second, this heating decomposes and volatizes the PS particles
thus separating the template particles from their overlying or shell-like
TiO2-based coatings. The rate of decomposition of the PS particles
at this juncture influences the porosity of the remaining niobium-doped
TiO2-based nanomaterial and ultimately provides it with a mesoporous
morphology; that is, a material comprising pore diameters in the range of
about two nanometers to about fifty nanometers.

[0013]In this configuration the partially-crystalline mesophase
constitutes an efficient and effective catalyst substrate.

[0014]For even broader utility of the mesophase substrate a second,
higher-temperature heat treatment may now be carried out to promote
further conversion of the TiO2 into its rutile crystalline phase
while also reducing some TiO2 into lower oxidation state titanium
oxides. These lower oxidation state titanium oxides, such as
Ti4O7, have more free active electrons available for transport
through a crystalline structure and thus help improve the electrical
conductivity of the catalyst support material rendering it more suitable
as a support material in highly acidic fuel cell environments.

[0015]While these mesoporous rutile TiO2 materials were devised for
PEM fuel cell applications they may be used in other catalyst
applications where their porosity, specific surface area, and low
electrical resistivity may be utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a cross-sectional view of a PEM fuel cell having an anode
layer and a cathode layer that may comprise the catalyst support material
of this invention.

[0017]FIG. 2 is flowchart diagramming some of the steps for synthesizing
the catalyst support material of this invention.

[0018]FIG. 3 is a transmission electron microscopy image showing the
mesoporous morphology of the catalyst support material after the first
heat treatment but before the second heat treatment of the synthesis
procedure diagramed in FIG. 2.

[0019]FIG. 4 is a transmission electron microscopy image showing the
presence of three pore types in the catalyst support material shown in
FIG. 3.

[0020]FIG. 5 is an X-ray diffraction diagram showing the appearance of the
TiO2 rutile crystalline phase after the first heat treatment of the
synthesis procedure diagramed in FIG. 2.

[0021]FIG. 6 is a transmission electron microscopy image showing the
porous morphology of the catalyst support material after the second heat
treatment, but before catalyst loading, of the synthesis procedure
diagrammed in FIG. 2.

[0022]FIG. 7 is an X-ray diffraction diagram showing the titanium oxides
present, including those of the rutile TiO2 phase and the lower
oxidation state Ti4O7, after the second heat treatment of the
synthesis procedure diagrammed in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0023]In this section, attention will be focused on the specific
processing of a mesoporous catalyst support material comprised primarily
of rutile crystalline TiO2 with enhanced electrical conductivity
with particular application for fuel cells. This specific high
conductivity catalyst support material often requires two thermal
treatments, the second of which is used to increase the conductivity of
the support. Thus this support may, after only the initial thermal
treatment, be employed as a catalyst support where the enhanced
electrical conductivity imparted by the second thermal treatment is not
required.

[0024]Fuel cells--such as PEM fuel cells--have generally been outfitted
with electrocatalyst-containing electrode layers that include finely
divided carbon powders as a catalyst support material. But the highly
acidic and otherwise corrosive nature of fuel cells often degrades these
carbon materials; incidents that can disturb optimal fuel cell operating
conditions and lead to, among others, efficiency losses. Catalyst support
materials having TiO2 as their main constituent, on the other hand,
are more corrosion resistant than typical carbon powders. But these
materials are not quite as electrically conductive as carbon and have
proven difficult to synthesize with a morphology (surface
characteristics) that meets the minimal desired criteria associated with
fuel cell electrode applications. To address these and other related
issues, a synthesis technique has been developed that can fabricate a
TiO2-based catalyst support material that exhibits a mesoporous
morphology and an electrical conductivity comparable to that of its
carbon counterpart. This material can thus help improve the service life
of fuel cell electrodes as well as the efficiency of the fuel cell.

[0025]FIG. 1 shows, in a simple illustrative manner, a PEM fuel cell 10
that may be combined in series with many other fuel cells of similar
construction to form a fuel cell stack (not shown) capable of generating
a relatively high power density. The fuel cell 10 shown here includes a
membrane electrode assembly (MEA) 12 sandwiched between opposed gas
diffusion media (GDM) layers 14, and a bipolar plate 16 disposed adjacent
to each GDM layer 14 opposite the MEA 12. The construction and operation
of such a fuel cell 10 and its individual components is generally well
understood by skilled artisans and, thus, need not be fully explained
here.

[0026]The MEA 12 is primarily composed of three components or
layers--namely, a solid polyelectrolyte membrane 18, an anode 20, and a
cathode 22. The polyelectrolyte membrane 18 is an ionically conductive
and electrically insulative polymer material that serves several
purposes. For instance, it allows protons generated at anode 20 to
migrate towards the cathode 22 through its polymer matrix; it forces
electrons generated at the anode 20 to travel through an external circuit
to reach the cathode 22; and it keeps the reactant gasses supplied to
each electrode separated. And there are many polyelectrolyte materials
available for such a purpose. For example, the MEA 12 may utilize a
membrane formed of one or more sulphonated fluoropolymers such as the
perfluorosulfonic acid copolymer available from DuPont under the trade
designation NAFION®. But of course the polyelectrolyte membrane 18
may be formed from other known proton conductive materials.

[0027]The anode 20 and the cathode 22 are in intimate contact with
opposite sides of the polyelectrolyte membrane 18. The anode 20
dissociates reactant gasses, such as hydrogen, into protons and electrons
while the cathode 22 facilitates the reaction of those protons and
electrons on the other side of the membrane 18 with supplied oxygen to
form water. To perform these tasks, both the anode 20 and the cathode 22
generally comprise electrocatalysts integrated within a structural binder
material of, for example, a polyelectrolyte material. The electrocatalyst
utilized here comprises catalyst particles carried on a catalyst support
material comprised primarily of TiO2 and doped, if desired, with a
transition metal element such as niobium, vanadium, manganese, iron,
molybdenum, tantalum, tungsten and rhenium in an amount from about 5 mole
percent to about 10 mole percent.

[0028]The catalyst support material, if doped, may thus be represented by
the formula Ti1-xMxO.sub.y with M being a transition metal
element, with x ranging from about 0.05 to about 0.10, and with y being
variable depending on the oxidation state of the transition metal. The
TiO2 of this material is primarily arranged in its rutile
crystalline microstructure thus providing the material with enhanced
electrical conductivity as compared to its non-conductive anatase phase.
The TiO2 catalyst support material also exhibits a mesoporous
morphology and can thus achieve acceptable surface area and porosity
characteristics so as to ensure that a large concentration of three-phase
boundary reaction sites are available for reactant/catalyst particle
interaction. As has been noted previously, in this form the support is
suitable for application as a catalyst support where the enhanced
electrical conductivity imparted by subsequent processing is not a
requirement. Examples of catalyst particles that can be supported on such
a support material include, but are not limited to, platinum, palladium,
and platinum alloys such as those containing molybdenum, cobalt,
ruthenium, nickel, tin, or other suitable transition metals.

[0029]A synthesis technique for forming the catalyst support material just
described and being doped with niobium is shown schematically in FIG. 2.
First, as depicted in step 30, there is provided decomposable polymer
template particles, an amount of a titanium precursor alkoxide, and a
doping amount of a niobium precursor alkoxide. The polymer template
particles may be spherical polystyrene (PS) particles sized around 200
nanometers in diameter. These are obtained as a 10 weight percent
dispersion in water. Adding the appropriate mass of PS particles to
anhydrous ethanol acidified with 3-4 drops of 5N nitric acid so that it
exhibits a pH around 3 necessarily also adds water to produce a
dispersion of PS in an acidified ethanol--water solution. The quantity of
water added will vary depending on the mass of polystyrene particles
added, ranging from 0.58 to 0.97 moles, and thus as Table 1 makes clear,
in all cases the water is present in molar excess. Other polymeric
materials of the appropriate size distribution may be suitable as well.
The acidified environment was solution of spherical nano-sized PS
solution. The role of the titanium and niobium precursor alkoxides
utilized here is to make available to the template a supply of Ti4+
and Nb5+ oxidation state metallic ions, respectively. Specific
examples of suitable precursor alkoxides include, but are not limited, to
titanium tetraisopropoxide [Ti(O(CH3)CHCH3)4)] and niobium
pentaethoxide [Nb(OC2H5)5]. The precursor alkoxides and
the PS template particles may be provided in quantities that satisfy two
conditions: (1.) the synthesized catalyst support material is doped with
niobium in an amount from about 5 mole percent to about 10 mole percent
of the titanium; and (2.) the weight ratio of PS particles to formed
oxides (of Ti and Nb) is between about 0.1 and about 0.3.

[0030]Next, in step 32, the precursor alkoxides are hydrolyzed into
hydrated titanium and niobium oxides. A general representation of this
reaction can be summarized by the following equations.

Ti(OR1)4+4H2O→Ti(OH)4+4R1OH

Nb(OR2)5+5H2O→Nb(OH)5+5R2OH

These hydrated oxides readily precipitate out of solution as a white gel
and deposit onto the surface of the PS template nanoparticles. The result
is a core-shell structure in which the "core" PS nanoparticles are coated
with a hydrated oxide "shell" that has a thickness of about a few
nanometers to about a few tens of nanometers. Normally the amount of
water present in the PS template suspension is sufficient to complete the
hydrolysis of both precursor alkoxides. Also, the presence of a
surfactant in the suspension at about one weight percent of the PS
particles may help enhance the deposition of the oxides onto the PS
template particles at this stage. Suitable surfactants include
hexadecyl-trimethylammoniumbromide (HATB) or any other macromolecule with
a hydrophobic hydrocarbon tail and a hydrophilic head that can decompose
without contaminating the suspension.

[0031]The coated template PS nanoparticles may now be collected as
depicted in step 34. A spray dryer, for instance, may be employed to
disperse, dry, and collect a significant portion (greater than 90%) of
the coated template PS particles by spraying the suspension at a high
nozzle temperature for evaporation of the alcohol and water under an
inert blanket gas of nitrogen. Nozzle temperatures of about 100°
C. to about 120° C. generally suffice. A very fine white powder is
the result of such a process.

[0032]The collected white powder may now be subjected to a first heat
treatment as shown in step 36. This heat treatment is performed in an
inert atmosphere at a temperature and duration so as to accomplish at
least two objectives. First, the hydrated oxide shell is dehydrated and
substantially converted into an amorphous anhydrous TiO2 and niobium
oxide shell, i.e., a Ti1-xNbxO.sub.y shell with
0.05≦x≦0.10 and y being variable. But, nonetheless, it has
been found that this heat treatment step 36 directly produces a modest
amount of the TiO2 in its rutile crystalline structure due to the
catalytic effects of niobium. More specifically, and without being bound
by any theory, it is thought that the presence of niobium lowers the
activation energy of the rutile TiO2 reaction pathway enough such
that some rutile TiO2 is formed instead of the generally more
energetically favorable anatase TiO2. Second, the template PS
nanoparticles are decomposed and volatized while the newly formed
Ti1-xNbxO.sub.y shell is further dried. The volatile compounds
formed from PS template degradation--namely hydrogen and hydrocarbon
vapors--burst through the Ti1-xNbxO.sub.y shell and are swept
away to provide the remaining oxide shell material with a variety of pore
types and an overall mesoporous morphology and an average pore size of
about 15 nm.

[0033]In particular, at least three types of pores have been identified in
the oxide material; the presence and appearance of which are dependent on
the rate of template PS decomposition. They include--in order from those
formed by a relatively rapid decomposition to a relatively slow
decomposition--widely open pores, ink-pot open pores, and closed pores.
These two objectives can be accomplished at temperatures around
500° C.

[0034]Then, as delineated in step 38, the material may be subjected to a
second heat treatment. This heat treatment may be carried out in a 100%
hydrogen atmosphere at a temperature and duration capable of providing
energy to promote the further arrangement of anatase TiO2 into its
more electrically conductive rutile crystalline phase. The hydrogen gas,
in conjunction with this higher temperature, also serves to reduce some
of the TiO2 into lower oxidation state titanium oxides that have
more free active electrons available for transport through a crystal
structure. As such, one result of this second heat treatment 38 is an
improved electrical conductivity of the Ti1-xNbxO.sub.y
material formed during heat treatment step 36. Another notable result of
the second heat treatment 38 is that the porosity and surface area of the
Ti1-xNbxO.sub.y material is enhanced due to contraction and
shriveling of this material under these relatively high temperatures.
While the specific temperature employed here is likely to be higher than
that used in heat treatment step 36, it is not as high as would normally
be required to fully convert TiO2 from its anatase state to its
crystalline rutile state. This is so because the direct formation of
rutile TiO2 during heat treatment step 36 helps minimize the energy
demands, and thus the temperature needed to meet those demands, of heat
treatment step 38. An appropriate temperature for this heat treatment may
be around 850° C.

[0035]The synthesized catalyst support material may now be loaded with a
suitable catalyst and incorporated into a fuel cell electrode by known
techniques.

[0036]The synthesis technique of FIG. 2 will now be described by way of
the following specific and non-limiting examples.

EXAMPLE

[0037]Nano-polystyrene (PS) particles measuring about 200 nm in diameter,
and their associated water dispersant, were thoroughly dispersed at
slightly different amounts into three sample solutions of 105 mL of
anhydrous ethanol, 5N nitric acid (HNO3), and
hexadecyl-trimethylammoniumbromide (HATB). The amount of PS particles
added to each sample solution was varied so that the three suspensions
would have a different weight ratio of polystyrene particles to the
product oxides (both Ti and Nb) which are deposited on the polystyrene
particles. Those weight ratios were 0.15, 0.20, and 0.25. The nitric acid
was added to each sample to lower its pH to around 3, and the HATB was
added to each sample in an amount equal to about one weight percent of
the PS particles. The resulting suspensions were then stirred vigorously
for about 30 minutes.

[0038]Next, solutions containing 0.025 moles of titanium tetraisopropoxide
and 0.002 moles of niobium pentaethoxide (corresponding to about 8 mol %
doping) were prepared for addition to each of the sample suspensions.
These solutions were prepared by dissolving 7 mL of stock 100% titanium
tetraisopropoxide and 0.5 mL of stock 100% niobium pentaethoxide into 100
mL of anhydrous ethanol. They were then added drop-wise with a
peristaltic pump to each of the acidified ethanol-PS suspensions and
stirred with a magnetic stirrer over the course of about two hours. The
initial addition rate was approximately 1 mL/minute and gradually
increased to about 2-2.5 mL/min as the reaction proceeded. The stirring
rate of the sample suspensions was also slightly increased over the
course of solution addition as rate of 300 RPM was used for the first
thirty minutes, a rate of 350 RPM was used for the next sixty minutes,
and a rate of 400 RPM was used for the final thirty minutes. The stirring
of the sample suspensions was continued for another thirty minutes at 400
RPM after the titanium tetraisopropoxide and niobium pentethoxide
solutions were fully added to the sample suspensions. A summary of what
has been added to each sample up to this point is summarized in Table 1
below.

[0039]Each sample was then injected into BUCHI B-290 mini spray dryer to
disperse, dry, and collect the coated template particles. The nozzle
temperature of the spray dryer was set at 120° C. and nitrogen was
used as a blanket gas. The spray drying process provided a collection
efficiency of over 90% and produced a very fine white powder in each
case.

[0040]The white powder of each sample was then subjected to a first heat
treatment at 500° C. in an argon atmosphere to remove the template
and convert the Ti and Nb hydrated oxides into Ti and Nb anhydrous
oxides. An inert gas stream was employed to sweep away the volatile
compounds produced during decomposition of the template PS particles. The
resulting material can now be said to have the general formula
Ti0.92Nb0.08O2.04 due to the presence of TiO2 and
Nb2O5, and its mesoporous morphology can be seen in the TEM
image of FIG. 3. FIG. 4 likewise shows a TEM image identifying the three
types of pores exhibited by the material that help it achieve this
morphology. As can be seen, (i.) widely open pores, (ii.) ink-pot open
pores, and (iii.) closed pores are all present. Furthermore an X-ray
diffraction diagram of the material, which is shown in FIG. 5, confirms
that the TiO2 present is at least partly configured in its
crystalline rutile phase. Such a conclusion can be drawn from the
appearance of specific rutile peaks at 27°, 36°, and
54° 2-theta. FIGS. 3, 4, and 5 are representative of what each
sample has produced up to this point.

[0041]After the first heat treatment, the material of each sample was
subjected to a second heat treatment at 850° C. in a hydrogen
atmosphere to promote further TiO2 arrangement into its rutile phase
while partially reducing some TiO2 into lower oxidation state
titanium oxides. FIG. 6 shows a TEM image of the mesoporous material
after this second heat treatment. And FIG. 7 shows an X-ray diffraction
diagram of the same material along with peak identifiers at those
specific peaks associated with the TiO2 rutile phase and the lower
oxidation state Ti4O7 oxide material. FIGS. 6 and 7 are
representative of what each sample has produced up to this point. As
such, it can be seen that the Ti0.92Nb0.08O2.04 material
that emerges from this second heat treatment has a mesophorous morphology
and is primarily comprised of rutile crystalline TiO2.

[0042]The morphology and the electrical conductivity of the synthesized
catalyst support material from each sample are summarized below in Tables
2 and 3, where the sample designations correspond with those associated
with the reactant listing in Table 1.

[0043]The data compiled in Tables 3 and 4 suggests that the synthesized
TiO2-based materials would be an effective catalyst support material
for a PEM fuel cell. For instance, the material synthesized in each
sample exhibits an electrical conductivity within two orders of magnitude
of common catalyst support carbon powder--which was measured at 0.22
Ω-cm. The surface area and porosity characteristics observed for
each sample are also comparable to traditional carbon support materials.

[0044]The above description of embodiments of the invention is merely
exemplary in nature and, thus, variations thereof are not to be regarded
as a departure from the spirit and scope of the invention.